Ignition-magneto for internal-combustion engines



H. ANDREINO.

IGNITION 'MAGNETO- FOR INTERNAL COMBUSTION ENGINES- APPLICATION FH ED MAR. 31. 1921i 1,379,953. Patented May 31,1921.

UNITED STATES PATENT OFFICE.

HECTOR ANDREINO, OF LE LQCLE, SWITZERLAND, ASSIGNGR TO THE SOCIETY FAB- RIQUES DES MOUTH-ES ZENITH SUCCESSE'UR DE FABRIQUES DES MOUTRES ZENITH GEORGES FAVRE-TACOT & 0113., OF LE LOCLE, SWITZERLAND.

IGNITION-MAGNETO FOR INTERNAL-COMBUSTION ENGINES.

Application filed March 31, 1921.

To all whom it may concern:

Be it known that I, I-lncron ANDREINO, a citizen of the Swiss Republic, and resident of Le Locle, Switzerland, have invented new and useful Improvements in Ignition- Magnetos for Internal-Combustion Engines, of which the following is a full, clear, and exact specification.

This invention relates to ignition magnetos for internal combustion engines and has for its object to provide an improved construction of field magnet with extended pole pieces embodying the features hereinafter described.

In certain types of ignition magneto as at present constructed, the pole face or angular pole pitch of each pole piece of the field magnet is defined, as shown for example in dotted lines on 1* igure 1 of the accompanying drawing, by two pole edges a subtending a certain polar angle a. the armature being assumed to be rotating for example in the direction of the arrow, the secondary current only attains a practically useful value during the very short interval of maximum variation of flux in the armature, that is to say when two of the diagonally opposite edges 6 of the armature are leaving the two corresponding edges a of the pole pieces of the field magnet. The secondary current can therefore be graphically represented by a curve having, in absolute values, maxima, each of which is defined by a very steep and closely adjacent sudden ascent and descent, and it is only on the very small portions of this curve in the neighborhood of the maxima, that the interruption of the secondary current can effect a practically useful result.

As ignition magnetos are generally so regulated that the current break for advance to ignition must take place at a maximum, or at least in its immediate neighborhood, the current break for lag to ignition necessarily takes place on the descending part of the curve for which the value of the secondary current is too weak to obtain an efiect which is in practice always sufficient, thus giving rise to well-recognized disadvantages in starting the engine.

The present invention has for its object to overcome these disadvantages and to obtain with retarded ignitionsufiicient current to produce an effective spark. Many con- When in operation,

Speeification of Letters Patent. Patented M 31 1921 Serial No. 457,349.

structions with field pole extensions have been proposed for this purpose, but none of them has the characteristics of the present invention, in which the extensions of the pole pieces of the field magnet have eccentrically curved faces which lie on the peripheral surface of geometrical cylinders the axes of which are parallel to the axis of rotation of the magneto and have an equal distance apart on either side of this axis, the diameters of these cylinders being equal to one another but less than the diameter of the bore of the pole pieces of the field magnet, so as to form between these curved extensions and the rotating element of the'magneto, an air gap which increases gradually from each pole edge to the outer end of its extension with the aforesaidobject of obtaining with retarded ignition, sufficient current; to produce an effective spark.

The construction of a magneto embodying the principle of the invention is illustrated by way of example in the accompanying drawing, in which Fig. 1 shows diagrammatically in end elevation the pole. pieces of the stationary field magnet and the ro tary armature of the magneto, while Fig. 2 is a cross section of a constructional form of a magneto according to the invention.

Referring now to the drawing, it will be seen that the magneto comprises a fixed field magnet A (Fig. 2) having pole pieces a and a rotating armature Z) of double T shape with the edges or corners at 6 The field magnet A is carried by a non magnetic frame D. The armature Z) is mounted on a shaft 01 the geometric axis of which is indicated at 0 in Fig. 1. It carries the usual induction coils s, 8 At the top of the magneto is arranged the usual current distributer f actuated from the armature shaft d and designed to furnish the current to the spark supplying circuit.

The pole pieces a are each provided with extensions '0 subtending an angle 8 beyond the usual pole edges a (F ig. 1), the pole faces of the four extensions 0 being eccentrically curved soas to lie in pairs on the peripheral surfaces of two geometrical cylinders having axes 0 parallel to the axis 0 and separated therefrom by equal, distances. The axes 0 are on different sides of the axis 0 and lie in the symmetrical plane separating the two pole pieces a, while the two cylindrical surfaces are of equal diameter less than the diameter of the bore of the pole pieces a. The air gap thus formed between each of these extensions 0 and the armature b as will be seen, increases gradually from the pole edge a to the outer edge of the extension. The zone of maximum variation of the flux in the armature is thus extended over the whole are of the polar extension, and this variation is thus less rapid and takes place during a longer period than in-the case of the usual construction of magneto. As a result of this arrangement, the current is represented by a curve the maxima of which, without being appreciably displaced as regards its abscissze, are lower than in the cases above mentioned, the

ascent being still steep but the descent be-' ing on the contrary much less rapid; the curve is thus much less peaked and has a more flattened form over the whole angle 8, the spark producing action of the break throughout this angle being very effective.

,Experience has shown that in this manner pieces can also be applied to magnetos having a stationary field magnet and armature and an intermediate rotating element, as well as to magnetos having a field magnet with more than two pole pieces.

What I claim is An ignition magneto for internal combustion engines comprising a field magnet, a rotary armature, pole pieces on said field magnet and extensions on said pole pieces having eccentrically curved faces, each pair of which lie on the peripheral surface of a geometrical cylinder having its axis parallei to the axis of rotation of the armature, the axes of the two cylinders being equally dis tant from the axis of rotation and the diameters of the two cylinders being equal to one another and less than the diameter of the bore of the pole pieces of the field magnet, so as to form between the said curved extensions and the armature of the magneto, an air gap which increases gradually from each pole edge to the outer edge of its extension, for the purpose specified.

In witness whereof I have hereunto signed my name this 14th day of -March, 1921, in the presence of two subscribing witnesses.

HECTOR ANDREINO.

lVitnesses FRIDA KUnz, AMAND BANNE. 

